This invention relates to the assembly of fuel injectors in engine heads and particularly to a tool for driving into place an injector of a hydraulically actuated fuel injection system.
Direct injection of fuel into individual combustion chambers of a diesel engine is a common practice. One type of fuel system for direct injection is referred to as a hydraulically actuated electronic unit injection (or HEUI) fuel system. In a HEUI system, fuel injectors send fuel under high pressure (e.g., at pressures up to greater than 20,000 psi) into the respective engine cylinders. In contrast to other xe2x80x9cmechanically actuatedxe2x80x9d (or MEUI) systems, a HEUI system includes a high pressure oil that acts in the injectors to elevate the fuel pressure from the low pressure it has before injection (e.g., about 60 psi) up to the injection pressure. A hydraulic oil supply pump is activated by a signal from an electronic control module (ECM) that controls a number of functions in the engine system.
HEUI system injectors formerly have been arranged with the high pressure oil entering the injector unit longitudinally, such as by a J tube that extends on top of an engine head. In such cases, the seals required for the injector to confine the fuel and the oil are relatively few (e.g., typically just two) and the injector unit has a configuration, including the seals, such that assembly by manually pushing the injector into an engine head has been convenient without a driving tool.
By way of further background, an injector for HEUI fuel systems that has allowed relatively easy hand insertion is shown and described in U.S. Pat. No. 5,499,612 by Haughney et al., which is incorporated herein by reference for its description relating to HEUI fuel systems. Such an injector is one that has an actuating fluid (e.g., engine oil) entering longitudinally into the injector body by way of a nonlinear line (sometimes referred to as a xe2x80x9cJ tubexe2x80x9d). The J-tube carries actuating fluid from a high pressure rail through a clamping assembly that is external to the main portion of the engine head. Experience has shown the J tube can sometimes fail and disable an injector. Alternative head and injector designs have been developed to avoid having a J tube subject to such failure. In such more advanced designs the high pressure fluid reaches the injector body from the high pressure rail through a passage in the head itself.
Use of different injector configurations of improved performance or reliability can give rise to issues about more numerous and complex seals and resulting impracticality of simple hand insertion of injectors into an engine head.
The invention provides a tool for driving injectors into assembled positions in an engine head. The injectors may be ones that have relatively numerous seals such as injectors receiving high pressure fluid at a location transverse to their major axis. The tool, for example, includes a pair of posts extending from a base member with each post having an extremity (or nib) remote from the base member that fits in a respective aperture of a fuel injector. The tool also has a handle extending from the base member opposite the posts with a striking surface for applying a blow, such as by a mallet, to drive an injector, with its variously configured seals, into an aperture of the engine head.
A method of the invention uses the tool in steps including, for example, aligning the injector with the injector aperture in the head; fitting the posts into fastener holes on the injector, grasping the handle on the base member of the tool, striking the striking surface of the handle to drive the injector into place, removing the tool, and then inserting fasteners to fix the injector to the head.
The tool and method of the invention allow easy assembly of relatively complex fuel injectors including those where highly pressurized oil enters the injector transverse to its centerline and have a relatively large number (e.g. six) seals for maintaining adequate confinement of the fuel and oil, respectively. The invention also allows easy assembly where the injector unit must be fit into the head at an angle (e.g., about 10xc2x0 or more from vertical) as is the case in some three-valve engine heads (i.e., two inlet air valves and one exhaust valve) or other heads where geometrical constraints impose a departure from vertical location of injectors.
These and other aspects of the invention will become more apparent from the following description.